Keroeides gracilis Whitelegge, 1897

Williams, Gary C., 2018, Illustrated Key and Synopses of Shallow-water Gorgonians and Pennatulaceans of the Central Philippines, Part 2 (Cnidaria: Anthozoa: Octocorallia), Proceedings of the California Academy of Sciences 64 (13), pp. 361-398 : 364-365

Keroeides gracilis Whitelegge, 1897

Figures 3 , 4

MATERIAL EXAMINED.— CASIZG 201396; Philippines, Occidental Mindoro, Lubang Island (13.77°N 120.12°E); ca. 34 m depth; 31 May 2014; coll. G.C. Williams; one whole colony wet-preserved in 95% ethanol.

REMARKS.— Colonies of this species are planar or nearly so, are copiously branched, and exhibit lateral branching. The calyces of the polyps are conspicuous and conical in shape, and are not particularly densely set or crowded on the branches. The sclerites of the outer coenenchyme are large spindles with relatively small tubercles that are uniformly-distributed over the sclerite surface. Due to the numerous and densely-disposed spindles of the surface of the colonies, these sea fans are relatively fragile or brittle, not exhibiting a high degree of flexibility without sustaining breakage of some branches. The tissues do not harbor zooxanthellae. The color of the colony examined here is brick red with pale yellow anthocodiae.

Kükenthal (1924) and Bayer (1949) consider Keroeides gracilis as a junior synonym of K. koreni Wright and Studer, 1889 . However, Grasshoff (1999) and Grasshoff and Bargibant (2001) disagree and maintain that they are separate species — K. gracilis from mesophotic reefs (30–164 m), red in color with yellow polyps, and K. koreni from deeper water (250–450 m), brick red in color throughout. I therefore concur with Grasshoff’s assessment and consider Keroeides gracilis to as the proper identification in this case.

SPECIES.— There are six described species in the genus. Color of the various species can vary from orange to deep red, or white to light grey or tan.

OCCURRENCE AND DISTRIBUTION.— The genus is widely distributed in the Indo-Pacific, Red Sea to Japan, New Caledonia, and Hawaii; usually encountered below 30 m, mostly in mesophotic depths or deep sea, rarely seen in shallower depths. Keroeides gracilis is widely distributed in and to the east of the Coral Triangle and is known from central Indonesia, the Philippines, New Guinea, Northern Mariana Islands, Palau, Tuvalu, and New Caledonia.

REFERENCES.— Bayer (1949, 1981); Fabricius and Alderslade (2001); Grasshoff (1999); Grasshoff and Bargibant (2001); Kükenthal (1924); Ofwegen (2010c).

Figures

FIGURE 3. Keroeides gracilis. A. Entire wet-preserved colony (CASIZ 201396); scale bar = 30 mm. B. Detail of lower portion of colony in A; scale bar = 10 mm.

FIGURE 4. Keroeides gracilis. Scanning electron micrographs of sclerites from the coenenchyme and calyces (CASIZ 201396). A-D, sclerites from the coenenchymal surface. E-N, sclerites from various calyces. Scale bar = 0.3 mm.